1. Field of the Invention
The present general inventive concept relates to an apparatus and method to revise a halftone image, and an image forming apparatus using the same. More particularly, the present general inventive concept relates to an apparatus and method to revise an edge of a halftone image, and an image forming apparatus using the same.
2. Description of the Related Art
Image forming apparatuses express images using binary values indicating whether a dot is printed, unlike image apparatuses, which express images using a multiple levels.
Therefore, image forming apparatuses convert an image expressed with multi-level values into an image expressed with binary values. This is called halftoning.
There are a wide range of halftoning methods, the most widely used of which is screening halftoning, which performs binary coding by comparing a gradation value of a pixel to be binary-coded ranging from 0 to 255 with a preset screen.
A screen may be either an amplitude-modulated (AM) screen or a frequency-modulated (FM) screen according to the method for constituting dots. An AM screen outputs dots in clusters, so dots can be output more securely than in an FM screen. For this reason, an AM screen is also referred to as a clustered screen, and is used for most image forming apparatuses.
In general, in an AM screen, an image with a low number of lines per inch (LPI) may be printed smoothly due to high dot representation but detailed printing is more difficult. An image with a high number of lines per inch (LPI) is able to be printed in greater detail, but smooth printing is more difficult.
Due to halftoning, edges of a the printed image may be rough.